A security system is active when persons are willing to have their activities monitored. Otherwise, the security system is passive.
Passive security systems typically use cameras, microphones and motion sensors. In passive systems, it is difficult to identify the persons in the environment being monitored. For example, a complex and expensive face recognition subsystem may need to be employed in the environment to identify people. This makes it difficult to deploy and maintain passive systems in large environments requiring, perhaps, hundreds if not thousands of cameras. In general, most conventional passive security systems are incapable of reliably identifying people in a large scale environment.
Active systems typically use access control panels, keyboards, fingerprint detectors, security cards, or badges to positively identify people in the environment. The problem with active systems is that it is difficult, if not impossible, to distribute identification means to a large population. If the environment is also accessible to the general public the positive pre-identification of all people is impossible. Also, the people in the environment often need to directly interact with an authentication device, which may be inconvenient.
Therefore, there is a need for an inexpensive and simple system that can concurrently distinguish between friend and foe in large environments.